An End-to-End Numerical Framework for Tidal Disruption Events with AthenaK

Abstract

In a tidal disruption event (TDE), a black hole (BH) tears apart a star, whose bound debris returns over many orbits to form an accretion disk. We present a framework built on the GPU-accelerated finite-volume code \texttt{AthenaK} that follows these stages in a single simulation with self-gravity throughout. We extend \texttt{AthenaK} with a moving frame, restart remapping between domains, an adaptive-mesh multigrid Poisson solver, a tabulated hydrogen--helium equation of state including recombination, a dual-energy update for the cold supersonic debris stream, a moving BH potential with excision, and localized adaptive time stepping (LAT), which speeds up the production run more than threefold. Each component is validated separately and in combination: the gravity solver maintains an isolated Lane--Emden sphere to a density error of $2.0\times 10^{-3}$ over 16.3 dynamical times, and dual-energy recovery reduces the pressure error of a Mach $7.75\times 10^7$ entropy wave from 15.7 to $4.0\times 10^{-12}$. We demonstrate the framework with a Newtonian $\beta =1$ disruption of a $1M_{\odot }$, $1R_{\odot }$ star by a $10^3{M}_{\odot }$ BH. The debris has the expected energy spread, insensitive to the self-gravity update interval, splits evenly into bound and unbound material, and yields a fallback rate approaching $t^{-5/3}$ at late times. At the pericenter nozzle, the thermal energy gained in the high-resolution run matches the vertical kinetic energy lost to within 6\%, whereas the fiducial run, with 4--8 times coarser cells, overheats the thinnest early stream through numerical dissipation. Their heating agrees to 10\% once the returning stream thickens. Multifrequency LTE post-processing produces synthetic images and luminosities.

29 pages, 18 figures, accepted by ApJS. Code available at https://github.com/HongxuanJiang/athenak-transients